Masters Degrees (Agronomy)
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Browsing Masters Degrees (Agronomy) by Subject "Boron"
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- ItemDie invloed van boor, trosvibrasie en relatiewe humiditeit van die trosatmosfeer op die bestuiwing van kweekhuistamaties (Lycopersicon esculentum L.)(Stellenbosch : Stellenbosch University, 2003-03) Smit, Johannes Nicolaas; Combrink, N. J. J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.ENGLISH ABSTRACT: In South Africa tomato production in greenhouses normally occurs out of season when conditions are unfavourable for production and for the pollination process. Pollination is of special importance and the backbone of production. High temperatures contribute to the formation of abnormalities in flower morphology such as splitting of the anther cone and style exsertion. Low temperatures inhibit growth of the anther cone and therefore the style is uncovered. The movement of pollen from the anther to the style is inhibited by the higher style position in relation to the anther cone. Under humid conditions the pollen tends to stick to the anther surface. Another factor contributing to the problem is the banning of European bumble bees in South Africa. Alternative methods of pollen transport have to be found. Truss vibration, honey bees and plant growth regulators (PGR) are the most popular alternatives. Truss vibration and the use of PGR's are labour intensive and honey bees tend to get disorientated inside a plastic greenhouse. During the first part of this study pollen from plants, grown at four different B-levels (0.02; 0.16; 0.32 and 0.64 mg rl) was germinated in vitro. It was kept at different temperatures and periods before incubating on different growth media. No proof was found that pollen from B-deficient plants germinated poorly. Germination of pollen decreased significantly after one week storage. Deterioration of pollen viability could be lowered by storage at 5°C. At least 10% sucrose is needed in the growth medium for in vitro germination but addition ofB had no positive effect. In a second phase of the study, the influence of the mentioned B application rates were tested. The experiment was done in a glasshouse where temperatures were mechanically regulated (22°C and 10°C day/night). Seedlings of the greenhouse tomato cultivar, Abigail, were planted in acid washed river sand. Plants were grown with the main stem trellised vertically and the side shoots removed weekly. Only the first, third and fourth cluster were used for this part of the study. The uptake of all the essential nutrient elements, fruit set, the relation of larger to smaller fruits, physical and chemical quality and fruit shelf life were evaluated. The application of B at higher rates increased the uptake of Ca and decreased K-uptake. Fruit set, fruit development, fruit color and shelf life were the best at a B-Ievel of 0.16 mg r'. At this rate the abortion of flowers was the least. The same plants were used for the second part of the study, using the third cluster. The influence of the same four B-Ievels, the relative humidity (RH) of the truss atmosphere and truss vibrations were tested. The second cluster was covered with a plastic bag. Dry {